Leader tape and magnetic tape cartridge using the same

ABSTRACT

A leader tape in which an non-magnetic under layer that contains a powder and a binder and a magnetic upper layer are sequentially laminated on at least one side of a support, a center line average roughness (Ra) of a surface of the support is from 30 to 50 nm, and a center line average roughness (Ra) of the multi layer coated surface is larger than that (Ra) of an opposite surface of the support, and the difference is at most 4 nm.

This application is based on Japanese Patent application JP 2004-091824,filed Mar. 26, 2004, the entire content of which is hereby incorporatedby reference. This claim for priority benefit is being filedconcurrently with the filing of this application.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a leader tape, to a magnetic tapecartridge in which the cartridge case rotatably houses a reel with amagnetic tape wound up therearound along with the leader tape bondedthereto.

2. Description of the Related Art

As magnetic tape cartridges used as recording media for external memorydevices for computers and others, heretofore known are those of a typewhere a magnetic tape is wound up around one or more reels rotatablyhoused in the cartridge case. Since the magnetic tapes are used for datastorage for computers and others and since important information isrecorded therein, the cartridges are specifically so designed that theyare free from a trouble of tape jamming and that a magnetic tape is notcarelessly led out of them.

In a single reel-type cartridge, a leader member such as a leader pin ora leader block is fitted to the top end of the magnetic tape, via whichthe magnetic tape is led out of the cartridge; or a leader tape isbonded thereto, which is formed of a relatively hard plastic materialand which has engage holes formed at the top end of the tape. For thecartridge of the type, a drive device is so constructed that themagnetic tape therein could be loaded/unloaded (draw out/wind up) whilethe leader member or the leader tape top end is held by the holdermember on the side of a recording and reproduction device.

In the loading/unloading process as above where the magnetic tape isdrawn out toward the side of the magnetic recording and reproductiondevice and its top end is wound up around the drive reel in the device,the top end of the magnetic tape is contacted with the tape guide andthe magnetic head disposed along the tape-running route, while notaccurately positioned relative to them, and in that condition, it ispulled and is therefore readily damaged. Accordingly, it is desirablethat the top end of the magnetic tape is reinforced.

In addition, the reinforcement is also desirable in order to prevent theleader block level difference occurring in the drive reel from beingtransferred onto a data-recording magnetic tape to increase the dropoutsin the tape. For this, a leader tape having a higher strength than thatof a magnetic tape is bonded to the top end of the magnetic tape (e.g.,see JP-A-2001-110164).

As a leader tape there is normally used a magnetic tape having a singlemagnetic layer.

Therefore, when the magnetic tape cartridge loaded in LTO drive issubjected to load/unload cycles, the surface of the leader tape whichrubs against LTO drive running system is scratched to give scrapingsthat are then attached to the running system. The scrapings that havebeen attached to the running system are then transferred to the surfaceof the magnetic tape, causing a rise of dropout. It is alsodisadvantageous in that deformation of the leader tape is transferred tothe magnetic tape, raising the error rate.

With the recent tendency for enhancement of capacity of magnetic tapecartridge, the recording density of the magnetic tape cartridge has beenraised. Thus, the problem of spacing loss due to transfer of deformationof leader tape to data recording magnetic tape has become moreremarkable. It has thus been desired to improve the related art leadertape and data tape.

The leader block mentioned above is so designed that it may be housed inthe recess formed in the core of a take-up reel, and when housedtherein, a part of the leader block forms a part of the arc face of thecore.

This is graphically illustrated. As in FIG. 4A, a leader block 40 isfitted into the recess 42 formed along the radial direction of the core41, and, for example, in this condition, the end face 40 a of the leaderblock 40 forms a part of the take-up face of the core 41. Asillustrated, the end face 40 a of the leader block 40 is curved like anarc in correspondence to the outer peripheral face of the core 41, inorder to smoothly wind up the magnetic tape MT around it.

However, in such a related art tape drive, the end face 40 a mayprotrude above the core 41, as in FIG. 4B, depending on the dimensionalaccuracy of the leader block 40 that constitutes a part of the take-upface, and it may form an unacceptable level difference in the take-upface of the core 41.

The level difference may cause folding or deformation of the leader tapeLT, and, as in FIG. 4C, the folding and the deformation occur similarlyalso in the part of the magnetic tape MT which is wound up as thesubsequent layers and which is to be a substantial recording region(this may be referred to as “tape deformation transfer”). The tapedeformation transfer may cause a problem in that a suitable distancebetween the tape and the recording/reproducing head could not be ensuredin the process of information recording/reproduction, and it maytherefore cause recording failure and information loss.

If the time for which the tape is kept wound up around a take-up reel isshort, then the tape deformation transfer would not cause the problemsas above, but when the magnetic tape MT is kept wound up around thetake-up reel and left as such for long, then the magnetic tape MT mayoften have a regular tape deformation transfer on the surface thereof,at a pitch of nearly the circumference length of the core 41.

SUMMARY OF THE INVENTION

An object of the invention is to provide a leader tape which cansuppress the increase in dropouts to be caused by transference of adrive reel or a leader block onto it during long-term storage orhigh-temperature running, and can prevent the decrease in outputs evenwhen repeating the loading/unloading process; and to provide a magnetictape cartridge using the leader tape.

The object of the invention can be attained by the following means:

1) A leader tape in which an non-magnetic under layer that contains apowder and a binder and a magnetic upper layer are sequentiallylaminated on at least one side of a support, a center line averageroughness (Ra) of a surface of the support is from 30 to 50 nm, and acenter line average roughness (Ra) of the multi layer coated surface islarger than that (Ra) of an opposite surface of the support, and thedifference is at most 4 nm.

2) The leader tape of above 1), wherein a thickness of the magneticupper layer is from 0.1 to 2.0 μm.

3) The leader tape of above 1) or 2), wherein a center line averageroughness (Ra) of the magnetic upper layer is from 15 to 40 nm.

4) The leader tape of any of above 1) to 3), wherein a back layer isformed on the opposite face of the support, and surface electricalresistances of the magnetic upper layer and the back layer each is atmost 10¹⁰ Ω/sq.

5) A magnetic tape cartridge where a magnetic tape is wound up aroundone or more reels rotatably housed in a cartridge case, in which aleader tape that is bonded to a top end of the magnetic tape and is letout toward a magnetic recording and reproduction device while leadingthe magnetic tape is the leader tape of any of above 1) to 4).

The leader tape of the invention is designed to have aspecifically-defined surface roughness, and therefore, when it is woundup, a suitable distance may be formed between the faces of the woundtape. The remarkable advantages of the leader tape of the type are that,since the pressure to it may be relieved, a leader block and others areprevented from being transferred to magnetic tapes. Also, The leadertape of the invention is designed to have a specifically-defineddifference in Ra between the two sides of the support, and therefore,when repeating the loading/unloading process, the tape deformation isprevented, and the decrease in output is also prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a constitutional view conceptually showing a magneticrecording and reproduction device used for the invention.

FIG. 2 is a perspective exploded view showing the magnetic tapecartridge used in the magnetic recording and reproduction device.

FIG. 3A is a perspective view of the drive reel used in the magneticrecording and reproduction device; FIG. 3B is a partly-enlargedcross-sectional view of FIG. 3A cut along the IIIB-IIIB line.

FIGS. 4A to 4C are explanatory views of a related art.

DETAILED DESCRIPTION OF THE INVENTION

The center line average roughness (Ra) of the support of the leader tapeaccording to the invention is from 30 to 50 nm.

“Ra” as referred to herein means a value measured with aphotointerference surface roughness meter (WYKO's HD-2000) under thecondition mentioned below.

-   -   Objective lens: 50-power, intermediate lens: 0.5-power, and        detection range: 242 μm×184 μm; and after cylindrical correction        and inclination correction, Ra is calculated.

In this arrangement, when the leader tape is wound on the reel, acushioning effect can be exerted to further inhibit deformationtransfer.

The leader tape of the invention is preferably used in a magneticrecording/reproducing device having a linear recording density of 100kfci or more and a difference of from 0 to 16 μm between the recordingtrack width and the reproducing track width. In some detail, since asystem having a difference of more than 16 μm between recording trackwidth and reproducing track width has a sufficiently great recordingtrack width as compared with reproducing track width, no rise of dropoutoccurs even tape deformation causes the occurrence of tape deviation ofseveral micrometers because the head runs over the recording track.However, a magnetic recording/reproducing device having a difference ofnot greater than 16 μm between recording track width and reproducingtrack width and hence a great linear recording density is subject toremarkable track dislocation due to tape deformation and thus is moresubject to tape deformation transfer. Accordingly, the advantage of theleader tape according to the invention becomes remarkable when amagnetic recording/reproducing device having a great linear magneticdensity is used.

Not specifically defined, the magnetic recording and reproduction devicemay be any one that comprises a magnetic tape cartridge and a magnetictape drive.

In addition, not also specifically defined, the magnetic tape cartridgemay be any one in which a magnetic tape with the leader tape of theinvention bonded thereto is wound up around one or more reels rotatablyhoused in the cartridge case. The invention produces better results whenapplied to single reel devices.

The leader tape of the invention may be bonded to the top end of amagnetic tape on and from which signals are recorded and reproduced, byattaching a known splicing tape thereto in such a manner that one end ofthe leader tape is butt-jointed with the top end of the magnetic tape.The other end of the leader tape is provided with an engaging membersuch as leader pin, and this is used for fixing the leader tape to thedrive reel of a magnetic recording and reproduction device.

In the magnetic recording and reproduction of the invention, themagnetic tape cartridge provided with the leader tape of the inventionmay be used in a magnetic recording and reproduction device, and itenables recording and reproduction under the condition where the linerecording density of the magnetic tape to which the leader tape isbonded is at least 100 kfci (preferably at least 200 kfci, morepreferably at least 300 kfci) and the difference between the recordingtrack width (preferably at most 20 μm, more preferably at most 15 μm)and the reproduction track width (preferably at most 10 μm, morepreferably at most 7 μm) is from 0 to 16 μm (preferably from 0 to 10 μm,more preferably from 2 to 8 μm).

The magnetic recording and reproduction using the leader tape and themagnetic tape cartridge of the invention prevents track shifting andenables stable recording and reproduction even when the recording trackwidth is narrow and the difference between the recording track width andthe reproduction track width is small like this.

The recording and reproduction device in which recording andreproduction is attained at the above-mentioned track width is notspecifically defined, for which are usable any known magnetic recordingand reproduction devices equipped with recording/reproduction heads.

The magnetic head for use in the invention is preferably an inductivehead for recording, and an MR head for reproduction.

The invention is described in more detail hereinunder.

[Leader Tape]

The magnetic upper layer and the non-magnetic under layer to be providedon the support are mainly composed of a dispersion of an inorganicparticulate material in a binder. The upper layer and the under layerare formed on the surface of the support which is to come in contactwith the magnetic head. The average particle size of the inorganicpowder to be used in the upper layer and the under layer is from 0.02 to1 μm, preferably from 0.05 to 0.6 μm. The form of the particles maybegrain, needle, tablet, cube or the like.

The purpose of providing the upper layer and the under layer is toprovide functions which are not possessed by the support, e.g., toincorporate abrasive particles in the surface of the support which is tocome in contact with the magnetic head and hence render the supportcapable of cleaning, to incorporate electrically-conductive particles inthe support and hence provide the support with antistat effect, toincorporate a magnetic material in the support and hence allow recordingof magnetic signal.

Preferably, a two-layer structure obtained by spreading the samenon-magnetic layer (under layer) and magnetic layer (upper layer) asused in the data tape is provided on the surface of the support which isto come in contact with the magnetic head while a back coat (back layer)mainly composed of carbon black is provided on the other surface of thesupport.

The central line average surface roughness Ra of the support of theleader tape is from 30 to 50 nm, preferably from 32 to 45 nm.

In this arrangement, when the leader tape is wound on the reel, acushioning effect can be exerted to further inhibit deformationtransfer. The surface roughness Ra of the support of the leader tape canbe easily predetermined by means such as change of calenderingconditions.

Further, it is necessary in the invention that Ra of the multi-layercoated surface of the support of the leader tape be greater than that ofthe other surface of the support and the difference in Ra between thetwo surfaces be 4 nm or less, preferably 2 nm or less. In thisarrangement, when subjected to cycles of load/unload, the leader tapecan be prevented from being deformed, making it possible to inhibitoutput drop.

The aforementioned requirements can be controlled by various methods.These requirements can be easily controlled, e.g., by making thetemperature different between the multi-layer coated surface and theother surface of the support during calendering in the process for theproduction of the support so that the heating conditions duringstretching differs from the multi-layer coated surface to the othersurface of the support.

The thickness of the upper layer is preferably from 0.1 to 2.0 μm. Bypredetermining the thickness of the upper layer within this range, aneffect of making it difficult for the magnetic layer to receive theshape of the drive reel or the leader block can be exerted.

The central line average surface roughness Ra of the upper layer ismeasured by the same method as used for Ra of leader tape. The centralline average surface roughness Ra of the upper layer is from 15 to 40nm, preferably from 20 to 30 nm. By predetermining Ra of the upper layerwithin this range, an effect of relaxing the transfer of the shape ofthe leader block, etc. to the magnetic tape and inhibiting thedeformation of tape after cycles of load/unload can be exerted.

The sum of the thickness of the upper and under layers is preferablyfrom 1.0 to 3.0 μm, more preferably from 1.5 to 2.5 μm. The thickness ofthe support is preferably from 3 to 17 μm, more preferably from 6 to 15μm.

The total thickness of the leader tape is preferably from 5 to 20 μm,more preferably from 8 to 18 μm.

Further, the surface electrical resistance of the leader tape (surfaceelectrical resistance of upper layer) and the surface electricalresistance of the back layer which is optionally provided each arepreferably 10¹⁰ Ω/sq or less, more preferably 10⁹ Ω/sq or less. In thisarrangement, the leader tape can be rendered antistatic to preventitself from being damaged by electrostatic charge generated on themagnetic head, making it possible to enhance reliability as well asdurability against cycles of load/unload of magnetic tape cartridgeobtained by assembly of leader tape essentially having a higher strengththan magnetic tape on magnetic recording/reproducing device.

As a method of controlling the aforementioned surface electricalresistance to a predetermined range there may be used a method involvingthe incorporation of an electrically-conductive particulate material inat least one of upper layer, under layer and back layer. For example,carbon black may be incorporated in an amount of from 1 to 20 parts byweight based on 100 parts by weight of the binder in the various layers.

Preferably, the leader tape is a magnetic tape that comprises anon-magnetic layer containing an inorganic powder and a binder as theunder layer and a magnetic layer containing a ferromagnetic powder and abinder as the upper layer, and has a back layer formed on the oppositeside thereto.

The leader tape that is the magnetic tape as above is described indetail hereinunder.

(Magnetic Layer)

<Binder in Magnetic Layer and Non-Magnetic Layer>

The binder to be used in the magnetic layer and the non-magnetic layermay be any of known thermoplastic resins, thermosetting resins, reactiveresins and their mixtures. The thermoplastic resin may have a glasstransition point falling between −100 and 150° C., a number-averagemolecular weight falling between 1000 and 200000, preferably between10000 and 100000, and a degree of polymerization falling between about50 and 1000 or so.

Examples of the resin of the type are polymers or copolymers comprisingconstitutive units of vinyl chloride, vinyl acetate, vinyl alcohol,maleic acid, acrylic acid, acrylate, vinylidene chloride, acrylonitrile,methacrylic acid, methacrylate, styrene, butadiene, ethylene, vinylbutyral, vinyl acetal, vinyl ether and the like; and polyurethaneresins, and various rubber-type resins. The thermosetting resin and thereactive resin include, for example, phenolic resins, epoxy resins,polyurethane-curable resins, urea resins, melamine resins, alkyd resins,acrylic reactive resins, formaldehyde resins, silicone resins,epoxy-polyamide resins, mixtures of polyester resins and isocyanateprepolymers, mixtures of polyester-polyols and polyisocyanates, andmixtures of polyurethanes and polyisocyanates. These resins aredescribed in detail in Plastic Handbook (published by Asakura Shoten).In addition, any known electron ray-curable resin may be used in eachlayer. Its examples and its production methods are described in JP-A62-256219.

The above-mentioned resins may be used herein either singly or ascombined. Preferably, at least one selected from polyvinyl chlorideresins, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylacetate-vinyl alcohol copolymers and vinyl chloride-vinyl acetate-maleicanhydride copolymers is combined with a polyurethane resin and apolyisocyanate for use in the invention.

The polyurethane resin may have any known structure ofpolyester-polyurethane, polyether-polyurethane,polyether-polyester-polyurethane, polycarbonate-polyurethane,polyester-polycarbonate-polyurethane, and polycaprolactone-polyurethane.Optionally but preferably, all these binders have at least one polargroup selected from COOM, SO₃M, OSO₃M, P═O(OM)₂, O—P═O(OM)₂ (in these, Mrepresents a hydrogen atom or an alkali metal base), OH, N(R)₂, N⁺(R)₃(where R represents a hydrocarbon group), epoxy group, SN and CN,introduced thereinto through copolymerization or addition reaction, inorder that the binders may realize further better dispersibility anddurability. The amount of the polar group in the binders may be from10⁻¹ to 10⁻⁸ mol/g, preferably from 10⁻² to 10⁻⁶ mol/g.

Preferably, the number of the hydroxyl groups to be in the polyurethaneresin is from 3 to 20 in one molecule, more preferably from 4 or 5 inone molecule. If the number is smaller than 3 in one molecule, then thereactivity of the resin with a polyisocyanate curing agent may lower andtherefore the film strength and the durability may lower. If, however,the number is larger than 20, then the solubility and the dispersibilityin solvent of the resin may lower. For controlling the content of thehydroxyl groups in the polyurethane resin, a compound having at leastthree functional hydroxyl groups may be used in producing thepolyurethane resin. Concretely, there are mentioned trimethylolethane,trimethylolpropane, trimellitic anhydride, glycerin, pentaerythritol,hexanetriol; as well as branched polyesters and polyether-esters having3 or more functional hydroxyl groups that are obtained from a dibasicstarting from a polyester-polyol described in JP-B 6-64726 and thecompound serving as a glycol component. Preferred for use herein aretri-functional compounds. Tetra- or more multi-functional compounds mayreadily gel in the reaction step.

The polyisocyanates usable herein are, for example, isocyanates such astolylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI),hexamethylene diisocyanate, xylylene diisocyanate,naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophoronediisocyanate, triphenylmethane triisocyanate; products of theseisocyanates with polyalcohols; and polyisocyanates produced throughcondensation of these isocyanates.

The amount of the binder to be in the magnetic layer and thenon-magnetic layer may be generally from 5 to 50% by weight, preferablyfrom 10 to 30% by weight of the ferromagnetic powder in the magneticlayer or of the non-magnetic inorganic powder in the non-magnetic layer.When a vinyl chloride-based rein is used, its amount may be from 5 to30% by weight and when a polyurethane resin is used, its amount may befrom 2 to 20% by weight; and the amount of the polyisocyanate to becombined with these is preferably from 2 to 20% by weight. For example,however, when head corrosion may occur owing to minor dechlorination, acombination of only polyurethane and isocyanate may be used.

In the magnetic tape of the type, the amount of the binder, theproportion of the vinyl chloride-based resin in the binder, the amountof the polyurethane resin, the polyisocyanate resin and other resins,the molecular weight and the polar group content of the resinsconstituting the magnetic layer, as well as various physical propertiesof the resins mentioned above may be optionally varied between thenon-magnetic layer and the magnetic layer, and they are rather optimizedin the respective layers. For this, employable are any known techniquesrelating to multi-layered magnetic layers. For example, when the binderamount is varied in each layer, it is effective to increase the binderamount in the magnetic layer so as to reduce the surface abrasion of themagnetic layer. In order to improve the head touch of the tape to heads,the binder amount in the non-magnetic layer may be increased so as tosoften the tape.

<Ferromagnetic Powder>

The ferromagnetic powder to be used in the magnetic layer is preferablya ferromagnetic alloy powder comprising a principal component of α-Fe.The ferromagnetic powder may contain any other atoms such as Al, Si, S,Sc, Ca, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, Au,Hg, Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr and B, in addition tothe predetermined atom. In particular, the powder preferably contains atleast one of Al, Si, Ca, Y, Ba, La, Nd, Co, Ni and B, in addition toα-Fe, more preferably at least one of Co, Y and Al.

The ferromagnetic alloy powder may contain a small amount of a hydroxideor an oxide. The ferromagnetic alloy powder for use herein may be anyone produced according to any known method. For producing it, forexample, the following methods may be mentioned: A method of reducing acomposite organic acid salt (principally oxalate) with a reducing vaporsuch as hydrogen; a method of reducing iron oxide with a reducing vaporsuch as hydrogen to obtain Fe or Fe—Co particles; a method of pyrolyzinga metal carbonyl compound; a method of adding a reducing agent such assodium borohydride, hypophosphite or hydrazine to an aqueous solution ofa ferromagnetic metal so as to reduce the metal; a method of vaporizinga metal in a low-pressure inert gas to obtain a fine powder of themetal. Thus obtained, the ferromagnetic alloy powder may be subjected toknown slow oxidation, for example, according to a method of dipping itin an organic solvent and then drying it; or a method of dipping it inan organic solvent, then introducing oxygen-containing gas into it so asto form an oxide film on the surface of the particles and thereafterdrying the particles; or a method of forming an oxide film on thesurface of the particles by controlling the partial pressure of theoxygen gas and the inert gas applied thereto, not using an organicsolvent. The ferromagnetic alloy powder thus processed in any of thesemethods may be used herein.

A hexagonal-system ferrite powder may also be used for the ferromagneticpowder to be in the magnetic layer. The hexagonal-system ferriteincludes, for example, barium ferrite, strontium ferrite, lead ferrite,calcium ferrite, and their substituted derivatives such asCo-substituted derivatives. Concretely, there are mentionedmagnetoplumbite-type barium ferrite and strontium ferrite, spinel-coatedmagnetoplumbite-type ferrite, partially spinel phase-containingmagnetoplumbite-type barium ferrite and strontium ferrite. They maycontain any other atoms such as Al, Si, S, Sc, Ti, V, Cr, Cu, Y, Mo, Rh,Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, P,Co, Mn, Zn, Ni, Sr, B, Ge and Nb, in addition to the predeterminedatoms. In general, substances with elements such as Co—Ti, Co—Ti—Zr,Co—Ti—Zn, Ni—Ti—Zn, Nb—Zn—Co, Sb—Zn—Co or Nb—Zn added thereto may beused.

(Non-Magnetic Layer)

The inorganic powder to be sued in the non-magnetic layer is anon-magnetic powder and may be selected, for example, from inorganiccompounds such as metal oxides, metal carbonates, metal sulfates, metalnitrides, metal carbides, metal sulfides. Carbon black may be added tothe non-magnetic layer so as to attain known effects of reducing thesurface resistivity Rs, reducing the light transmittance and obtaining adesired micro-Vickers hardness. When carbon black is added to the underlayer, then the layer may be effective for storing lubricant. Regardingits type, carbon black usable herein may be any of furnace black forrubber, thermal black for rubber, black for color, and acetylene black.Depending on the desired effect thereof, carbon black to be in the underlayer must optimize the characteristics mentioned below. When combinedin the layer, carbon black may exhibit its effect. In addition, thenon-magnetic layer may contain an organic powder depending on itsobject. Known techniques relating to the magnetic layer may apply to thelubricant, the dispersant, the additive, the solvent and the dispersionmethod in the non-magnetic layer.

[Additive]

The additives that may be in the magnetic layer and the non-magneticlayer may be those having a head-cleaning effect, a lubricating effect,an antistatic effect, a dispersing effect and a plasticizing effect.Concretely, those described in WO98/35345 may be used herein.

For the lubricant, for example, herein usable are monobasic fatty acidshaving from 10 to 24 carbon atoms, and their metal salts (e.g., with Li,Na, K, Cu); monofatty acid esters, difatty acid esters or trifatty acidesters of monobasic fatty acids having from 10 to 24 carbon atoms and atleast any one of mono, di, tri, tetra, penta or hexa-alcohols havingfrom 2 to 12 carbon atoms; fatty acid esters of monoalkyl ethers ofalkylene oxide polymers; and fatty acid amides having from 8 to 22carbon atoms. The fatty acids and alcohols may contain unsaturated bondand may be branched.

Specific examples of the fatty acids are capric acid, caprylic acid,lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid,oleic acid, elaidic acid, linolic acid, linolenic acid, isostearic acid.The esters include butyl stearate, octyl stearate, amyl stearate,isooctyl stearate, butyl myristate, octyl myristate, butoxyethylstearate, butoxydiethyl stearate, 2-ethylhexyl stearate, 2-octyldodecylpalmitate, 2-hexyldodecyl palmitate, isohexadecyl stearate, oleyloleate, dodecyl stearate, tridecyl stearate, oleyl erucate,neopentylglycol didecanoate, ethylene glycol dioleate.

(Back Layer)

Preferably, the back layer contains carbon black and an inorganicpowder. Regarding the binder and various additives to the back layer,referred to are those mentioned hereinabove for the magnetic layer andthe non-magnetic layer. The thickness of the back layer is preferablyfrom 0.1 to 1.0 μm, more preferably from 0.4 to 0.6 μm.

(Support)

The support for the magnetic tape is preferably a non-magnetic flexiblesupport. For this, usable are any known films of polyesters such aspolyethylene terephthalate, polyethylene naphthalate; as well aspolyolefins, cellulose triacetate, polycarbonates, aromatic or aliphaticpolyamides, polyimides, polyamidimides, polysulfones, polyaramids, andpolybenzoxazole. Of those, preferred are polyethylene terephthalatefilms and polyimide films. The support may be previously processed forcorona discharge treatment, plasma treatment, adhesiveness improvementtreatment, thermal treatment or dust removal treatment.

Preferably, the support has an elastic modulus in the machine directionof from 3.5 to 20 GPa, and an elastic modulus in the cross direction offrom 3.5 to 20 GPa. More preferably, the elastic modulus of the supportis from 4 to 15 in both the machine direction and the cross direction.

(Production Method)

The magnetic layer and the non-magnetic layer may be formed bydissolving or dispersing the above-mentioned components in a solvent toprepare coating compositions for these, and applying the compositions inorder on a support (web). The method may be either a wet-on-wet systemwhere the magnetic layer is formed while the underlying non-magneticlayer is still wet, or a wet-on-dry system where the magnetic layer isformed after the underlying non-magnetic layer is dried. Thus coated anddried, the web is suitably oriented, calendered and slit.

[Data-Recording Magnetic Tape]

The data-recording magnetic tape for use herein comprises a magneticlayer formed on a non-magnetic support, and optionally has a backcoat.One preferred embodiment of the tape comprises a non-magnetic underlayer and a magnetic upper layer formed on a support having a thicknessof from 2 to 9 μm, and has a backcoat formed on the opposite sidethereto. The constitutive elements of the magnetic tape are suitable tohigh-density recording, and the magnetic tapes described in JP-A2001-250219 and 2002-251710 are preferred examples for use herein.

[Magnetic Tape Cartridge]

The magnetic tape cartridge of the invention is so designed that amagnetic tape is wound up around one or more reels rotatably housed inthe cartridge case, and this is characterized in that the leader tapethat is bonded to the top end of the magnetic tape and is let out towarda magnetic recording and reproduction device while leading the magnetictape is the leader tape of the invention.

[Magnetic Recording and Reproduction Device]

The leader tape of the invention especially exhibits its remarkableeffect when used in a magnetic recording and reproduction device wherethe line recording density is at least 100 kfci and the differencebetween the recording track width and the reproduction track width isfrom 0 to 16 μm, and its effect is still more remarkable when it is usedin a magnetic recording and reproduction device where the differencebetween the recording track width and the reproduction track width is atmost 10 μm.

Preferably, the thickness of the leader tape is at most 5 times that ofthe magnetic tape, more preferably at most 3 times, even more preferablyat most 2 times.

Also preferably, the length of the leader tape is not shorter than thelength corresponding to at least 3 windings of the drive reel in themagnetic recording and reproduction device, plus the tape running routelength from the mouth of the cartridge case to the drive reel.

One embodiment of the magnetic recording and reproduction device usedfor the invention is described in detail with reference to the drawingsattached hereto. Of the drawings that are referred to herein, FIG. 1 isa constitutional view conceptually showing one embodiment of therecording and reproduction device of the invention; FIG. 2 is aperspective exploded view showing the magnetic tape cartridge used inthe magnetic recording and reproduction device; FIG. 3A is a perspectiveview of the drive reel (take-up reel) used in the magnetic recording andreproduction device; FIG. 3B is a partly-enlarged cross-sectional viewof FIG. 3A cut along the IIIB-IIIB line. The magnetic recording andreproduction device of this embodiment comprises a magnetic tapecartridge with a magnetic tape wound up around one cartridge reel(let-off reel) and a magnetic tape drive (tape drive) loaded with themagnetic tape cartridge, and this is used in the magnetic recording andreproduction method described hereinunder.

As in FIG. 1, the magnetic recording and reproduction device 1 comprisesa magnetic tape cartridge 10 and a magnetic tape drive 20. In themagnetic recording and reproduction device 1 of the type, the magnetictape MT wound up in the magnetic tape cartridge 10 is let off and takenby the drive reel of the magnetic tape drive 20 that serves as a tapereceiver, or the magnetic tape MT thus wound up around the drive reel 20is unwound toward the cartridge reel (let-off reel) 11, wherebyinformation is recorded on the magnetic tape MT or the information thusrecorded on the magnetic tape MT is reproduced.

As in FIG. 2, the magnetic tape cartridge 10 satisfies the LTO Standard,and this has a cartridge case 2 divided into a lower half 2B and anupper half 2A. Inside it, the cartridge case 2 houses a single cartridgereel 11 around which a magnetic tape MT is wound up; a reel lock and acompression coil spring 5 for keeping the rotation of the cartridge reel11 locked; a release pad 6 for releasing the locked condition of thecartridge reel 11; a slide door 2D for opening and closing the magnetictape let-off mouth 2C formed on one face of the cartridge case 2 toextend to both the lower half 2B and the upper half 2A; a twisted coilspring 7 for forcedly pushing the slide door 2D toward the closingposition of the magnetic tape let-off mouth 2C; a miserasure preventingclaw 8; and a leader pin rack 9 formed near the magnetic tape let-offmouth 2C. A leader tape LT is bonded to the top end of the magnetic tapeMT. The magnetic tape MT in FIG. 2 is the leader tape LT.

The magnetic tape cartridge 10 is loaded in the magnetic tape drive 20,as in FIG. 1, and the leader tape LT is let out by the leader block 31which will be described hereinunder, and the leader block 31 is fittedinto the recess 23 formed in the core 22 of the drive reel 21 in themagnetic tape drive 20. Accordingly, the leader tape TL from themagnetic tape cartridge 10 may be thereby wound up around the core 22 ofthe drive reel 21.

The leader tape LT and the magnetic tape MT used in the magnetic tapecartridge 10 of this embodiment are described in detail.

The leader tape LT is formed long, and in this embodiment, its length isenough to correspond to at least 3 windings around the core 22 of thedrive reel 21 in the magnetic tape drive 20. The leader tape LTpreferably has a length of from 0.5 to 5.0 m, more preferably 0.9 m.

Next described is the magnetic tape drive 20.

The magnetic tape drive 20 comprises a spindle 24, a spindle drive unit25 for driving the spindle 24, a magnetic head H, a drive reel 21, atake-up reel drive unit 26 for driving the drive reel 21, and a controlunit 27, as in FIG. 1.

In addition, the magnetic tape drive 20 is provided with a leader block31 capable of engaging with the leader pin (see FIG. 2) disposed at thetop end of the leader tape LT from the magnetic tape cartridge 10, andthe leader block 31 is moved toward the magnetic tape cartridge 10 by alead-off mechanism (not shown) including a lead-off guide 32 or thelike.

When data are recorded/reproduced on/from the magnetic tape MT, thespindle drive unit 25 and the take-up reel drive unit 26 act to rotateand drive the spindle 24 and the drive reel 21, whereby the magnetictape MT is moved.

The drive reel 21 is so designed that the upper face of the lower flange21 a has radial grooves 21 b formed at regular intervals, as in FIGS. 3Aand 3B. The grooves 21 b function as discharge paths for discharging theair that may enter the drive reel 21 while the magnetic tape MT is woundup around it.

The action of the magnetic tape drive 20 is described.

When the magnetic tape cartridge 10 is set in the magnetic tape drive 20as in FIG. 1, then the lead-off guide 32 (see FIG. 2) acts to lead outthe leader pin 30 and move it to the drive reel 21 via the magnetic headH, and the leader block 31 is thereby fitted into the recess 23 of thecore 22 of the drive reel 21. The recess 23 is provided with an anchorpart (not shown) that engages with the leader block 31 to therebyprevent the leader block 31 from jumping out of the recess 23.

With that, the spindle drive unit 25 and the take-up reel drive unit 26are driven while controlled by the control unit 27, and the spindle 24and the drive reel 21 are rotated in the same direction so that theleader tape LT and the magnetic tape MT are moved toward the drive reel21 from the cartridge reel 11. Accordingly, the leader tape LT is woundup around the drive reel 21, and then the magnetic tape MT is wound uparound the drive reel 21, whereupon information is recorded on themagnetic tape MT or the information recorded on the magnetic tape MT isreproduced by the action of the magnetic head H.

When the magnetic tape MT is rewound around the cartridge reel 11, thespindle 24 and the drive reel 21 are rotated and driven in the directionopposite to the above, whereby the magnetic tape MT is moved toward thecartridge reel 11. Also in the rewinding operation, informationrecording on the magnetic tape MT or information reproduction from themagnetic tape MT may be attained by the magnetic head H.

In the magnetic recording and reproduction device 1 of the type, themagnetic tape MT is generally kept wound in the magnetic cartridge 10 inmany cases, but in some use embodiment, it may be kept wound up aroundthe drive reel 21 in the magnetic tape drive 20 for a long period oftime. In some such use embodiment, the usefulness of preventing tapedeformation transfer is extremely great, and the leader tape and themagnetic tape cartridge employed in the magnetic recording andreproduction device 1 of this embodiment and the magnetic recording andreproduction method for the device 1 are favorable for the case.Specifically, when the magnetic tape MT is wound up around the drivereel 21 of the magnetic tape drive 20 from the magnetic tape cartridge10, the leader block 31 that acts to lead the magnetic tape MT out ofthe magnetic tape cartridge 10 is fitted into the core 22 of the drivereel 21, but depending on the dimensional accuracy of the leader block31, the leader block 31 may protrude (as level difference) from the edgeface of the core 22. In such a case, when a related art leader tape iswound up around the drive reel 21, then the level difference may betransferred to the magnetic tape MT and the distance between themagnetic head and the magnetic layer maybe enlarged, therefore causingsome problems of recording failure and information loss in the magnetictape MT.

Contrary to this, in the magnetic recording and reproduction method ofthe invention, the level difference can be well absorbed by the leadertape LT, and even when the magnetic recording and reproduction device 1is used, in which the line recording density is at least 100 kfci andthe difference between the recording track width and the reproductiontrack width is from 0 to 16 μm, the method of the invention enjoys theadvantage in that it can evade the problems of recording failure andinformation loss in the magnetic tape MT.

EXAMPLES

The invention is described in detail with reference to the followingExamples, to which, however, the invention should not be limited.

Example 1

In the Examples, “part” is by weight.

Formation of Leader Tape:

<Preparation of Coating Compositions>

Coating Composition for upper layer: Ferromagnetic metal powder 100parts coercive force Hc: 128 kA/m (1600 Oe) specific surface area by BETmethod: 53 m²/g crystallite size: 160 angstroms saturation magnetizationσs: 130 A · m²/kg mean major axis length: 130 nm mean acicular ratio:6.5 pH: 9.3 Co/Fe: 5 atm. % Al/Fe: 7 atm. % Y/Fe: 2 atm. % soluble Na: 5ppm soluble Ca: 1 ppm soluble Fe: 1 ppm Vinyl chloride-based copolymer(Nippon Zeon's MR-100) 10 parts (—SO₃Na content: 5 × 10⁻⁶ eq/g, degreeof polymerization: 350), epoxy content: 3.5 weight % as monomer unit)Polyester-polyurethane resin 2.5 parts (neopentylglycol/caprolactonepolyol/MDI = 0.9/2.6/1 by weight, —SO₃Na content: 1 × 10⁻⁴ eq/g)α-alumina (mean particle size: 0.3 μm) 10 parts Carbon black (meanparticle size: 0.10 μm) 1 part Butyl stearate 1.5 parts Stearic acid 0.5parts Methyl ethyl ketone 150 parts Cyclohexanone 50 parts Toluene 40parts Coating Composition for under layer: Non-magnetic powder, TiO₂ 90parts specific surface area by BET method: 45 m²/g mean grain diameter:0.1 μm pH: 6.5 soluble Na: 5 ppm soluble Ca: 1 ppm Carbon black 10 partsmean primary particle size: 16 nm DBP oil absorption: 80 ml/100 g pH:8.0 specific surface area by BET method: 250 m²/g Vinyl chloride-basedpolymer 12 parts Nippon Zeon's MR-100 Polyester-polyurethane resin 5parts (neopentylglycol/caprolactone polyol/MDI = 0.9/2.6/1 by weight,—SO₃Na content: 1 × 10⁻⁴ eq/g) Butyl stearate 1.06 parts Stearic acid1.18 parts Methyl ethyl ketone 150 parts Cyclohexanone 50 parts Toluene40 parts

The constitutive components of the upper layer coating composition andthose of the under layer coating composition were separately kneaded ina continuous kneader and then dispersed by the use of a sand mill. 5parts of polyisocyanate (Nippon Polyurethane's Coronate L) was added toeach of the resulting dispersions, and 40 parts of methyl ethyl ketonewas added to each of them. The dispersions were filtered through afilter membrane having a mean pore size of 1 μm, and the upper layercoating composition and the under layer coating composition were thusobtained.

Coating Composition for Back Layer Formation:

Particulate carbon black 100 parts (Cabot's BP-800, mean particle size:17 nm) Coarse carbon black 10 parts (Carncalp's thermal black, meanparticle size: 270 nm) α-alumina (hard inorganic powder) 5 parts (meanparticle size: 200 nm, Mohs' hardness: 9) Nitrocellulose resin 140 partsPolyurethane resin 15 parts Polyester resin 5 parts Dispersant: copperoleate 5 parts Copper phthalocyanine 5 parts Barium sulfate(precipitating) 5 parts (BF-1, mean particle size: 50 nm, Mohs'hardness: 3, by Sakai Kagaku Kogyo) Methyl ethyl ketone 1200 parts Butylacetate 300 parts Toluene 600 parts

The constitutive components of the back layer coating composition werekneaded in a continuous kneader and then dispersed by the use of asandmill. 40 parts of polyisocyanate (Nippon Polyurethane's Coronate L)and 1000 parts of methyl ethyl ketone were added to the resultingdispersion, and this was filtered through a filter membrane having amean pore size of 1 μm to prepare a back layer coating composition.

Formation of Leader Tape:

The upper layer coating composition and the under layer coatingcomposition thus obtained in the above were applied at the same time toa long-size polyethylene terephthalate (PET) support (thickness: 14.0μm, Young's modulus in MD direction: 500 kg/mm² (4.9 GPa), Young'smodulus in TD direction: 500 kg/mm² (4.9 GPa), center line averageroughness Ra of the upper layer-coated face (cutoff value: 0.25 mm): 38nm, Ra of the back layer-coated face: 36 nm) in a mode of simultaneouscoating to form an upper layer and a under layer so that they could havea dry thickness of 0.8 μm and 1.8 μm, respectively. Next, while theupper layer was still wet, this was oriented by the use of a cobaltmagnet having a magnetic force of 300 mT and a solenoid having amagnetic force of 150 mT. Next, this was dried, and the upper layer wasthus formed.

Next, on the other face of the support (opposite side to the upperlayer), the back layer coating composition was applied to form a backlayer so that it could have a dry thickness of 0.5 μm. Then, this wasdried and the back layer was formed. Accordingly, a leader tape roll wasthus obtained, having the upper layer on one face of the support andhaving the back layer on the other face thereof.

The web was allowed to run through a 110° C. heat treatment zone for 5seconds under a tension of 1.5 Kg/m (14.7 N/m) so that it was subjectedto heat treatment.

The roll of leader tape thus heat-treated was passed through a 7-stagecalendering machine comprising a hot metal roll and an elastic rollhaving a core metal covered by a thermosetting resin (temperature: 90°C.; linear pressure: 300 Kg/cm (294 kN/m); speed: 300 m/min) so that itwas calendered, and then wound under a tension of 5 Kg/m (49 N/m). Thehot metal roll was made of chrome-molybdenum steel plated with hardchromium. The surface roughness Ra of the hot metal roll was 0.005 μm(cutoff value: 0.25 mm). The thermosetting resin constituting theelastic roll was obtained by reacting a work of bis (2-oxoline) with anaromatic diamine and an epoxy compound.

The roll thus obtained was then subjected to heat treatment at 50° C.for 48 hours. Subsequently, the roll was slit into a size of ½ inchwide, and then passed through a solenoid having a magnetic flux densityof 300 mT to undergo demagnetization.

[Preparation of Magnetic Tape Cartridge]

The ½ inch wide magnetic tape thus obtained was connected as a leadertape to a commercially available LTO tape to prepare a magnetic tapecartridge. The magnetic tape was wound over a length of 580 m.

Example 2

A magnetic tape cartridge according to the invention was prepared in thesame manner as in Example 1 except that as the support to be used in thepreparation of leader tape there was used a PET support having a centerline average roughness Ra of multi-layer coated face of 31 nm and an Raof the opposite face of 30 nm.

Example 3

A magnetic tape cartridge according to the invention was prepared in thesame manner as in Example 1 except that as the support to be used in thepreparation of leader tape there was used a PET support having a centerline average roughness Ra of multi-layer coated face of 49 nm and an Raof the opposite face of 45 nm.

Comparative Example 1

A magnetic tape cartridge was prepared in the same manner as in Example1 except that as the support to be used in the preparation of leadertape there was used a PET support having a center line average roughnessRa of multi-layer coated face of 8 nm and an Ra of the opposite face of8 nm.

Comparative Example 2

A magnetic tape cartridge was prepared in the same manner as in Example1 except that as the support to be used in the preparation of leadertape there was used a PET support having a center line average roughnessRa of multi-layer coated face of 30 nm and an Ra of the opposite face of38 nm.

Comparative Example 3

A magnetic tape cartridge was prepared in the same manner as in Example1 except that as the support to be used in the preparation of leadertape there was used a PET support having a center line average roughnessRa of multi-layer coated face of 25 nm and an Ra of the opposite face of28 nm.

Comparative Example 4

A magnetic tape cartridge was prepared in the same manner as in Example1 except that as the support to be used in the preparation of leadertape there was used a PET support having a center line average roughnessRa of multi-layer coated face of 54 nm and an Ra of the opposite face of50 nm.

Comparative Example 5

A magnetic tape cartridge was prepared in the same manner as in Example1 except that as the support to be used in the preparation of leadertape there was used a PET support having a center line average roughnessRa of multi-layer coated face of 40 nm and an Ra of the opposite face of32 nm.

Comparative Example 6

A magnetic tape cartridge was prepared in the same manner as in Example1 except that only the upper layer coating compound was spread over thesupport to a thickness of 2.6 μm.

[Evaluation of Magnetic Tape Cartridge]

[Tape Deformation]

The magnetic tape cartridge thus obtained was subjected to 10,000 cyclesof load/unload using LTO remodeled drive at a temperature of 23±2° C.and a relative humidity of from 40 to 60% RH. Thereafter, thedeformation of the magnetic tape was determined by a three-score method.

3 points: No deformation

2 points: A little deformation

1 point: Obvious deformation

[Output Decrease]

At first, whole length of the magnetic tape was made to run one cycle byusing the LTO remodeled drive to record the signal and measure thereproduction output. Then, the magnetic tape was subjected to 10,000cycles of load/unload, and the whole length of the magnetic tape wasagain made to run one cycle to measure the reproduction output. Thedifference in the reproduction outputs of 10 m of the magnetic tape towhich the leader tape was bonded, in which the signal was recorded,between the beginning state and that of after the load/unload wasdefined as the output decrease.

The results are set forth in Table 1 below.

TABLE 1 Surface Surface roughness electrical Surface of supportresistance roughness Ra (nm) Rs (Ω/sq) of Deformation Output multi-layeropposite upper back upper layer of leader decrease side side layer layerRa (nm) tape (dB) Example 1 38 36 5 × 10⁸ 8 × 10⁷ 24 3 −1 Example 2 3130 5 × 10⁸ 8 × 10⁷ 18 2 −2 Example 3 49 45 5 × 10⁸ 8 × 10⁷ 38 3 0Comparative 8 8 5 × 10⁸ 8 × 10⁷ 5 1 −6 Example 1 Comparative 30 38 5 ×10⁸ 8 × 10⁷ 18 1 −5 Example 2 Comparative 25 28 5 × 10⁸ 8 × 10⁷ 12 1 −5Example 3 Comparative 54 50 5 × 10⁸ 8 × 10⁷ 45 1 −4 Example 4Comparative 40 32 5 × 10⁸ 8 × 10⁷ 30 1 −4 Example 5 Comparative 38 36 5× 10⁸ 8 × 10⁷ 20 1 −4 Example 6

As can be seen in the aforementioned results, the inventive examplesshow a less deformation of magnetic tape and the output decrease issuppressed compared with the comparative examples.

1. A leader tape comprising: a support; and a multi layer comprising an non-magnetic under layer that contains a powder and a binder; and a magnetic upper layer in this order on a first surface of the support, wherein the first surface has a first center line average roughness of from 30 to 50 nm, a second surface of the support which it opposite side to the first surface has a second center line average roughness of from 30 to 50 nm, and the first center line average roughness is larger than the second center line average roughness and a difference thereof is 4 nm or less.
 2. The leader tape according to claim 1, wherein the magnetic upper layer has a thickness of from 0.1 to 2.0 μm.
 3. The leader tape according to claim 1, wherein the magnetic upper layer has a surface having a center line average roughness of from 15 to 40 nm.
 4. The leader tape according to claim 1, wherein the leader tape further comprises a back layer on the second surface of the support, and the magnetic upper layer and the back layer each has a surface electrical resistance of 1010 Ω/sq or less.
 5. A magnetic tape cartridge where a magnetic tape is wound up around one or more reels rotatably housed in a cartridge case, in which a leader tape that is bonded to a top end of the magnetic tape and is let out toward a magnetic recording and reproduction device while leading the magnetic tape is the leader tape of claim
 1. 